Heater for pressure switch

ABSTRACT

A flexible diaphragm-type pressure switch sensitive to light pressures on the order of 7 ounces to 11 ounces for use in freezing, moist atmospheres containing plant particles such as husks, cracked seeds and leaves which are likely to cake and freeze on the diaphragm, thus rendering the diaphragm insensitive to its designed pressures. A thermostatically controlled heating element is incorporated in the switch without changing the external dimensions of the switch, the heating element preventing freezing of moisture on the diaphragm and drying the plant particles accumulated thereon so that they can be carried away by air currents.

United States Patent 1451 May 23, 1972 Alms 154] HEATER FOR PRESSURE SWITCH [72] Inventor: Erhard E. Alms, 419 Valencia Avenue,

' Harrington, 111. 60010 [22] Filed: Aug. 10, 1970 1211 Appl. No.: 62,291

[52] U.S.Cl.. ..337/2,200/61.21,219/209, 337/377 [51] lnt.Cl. ..H0lh 31/00 [58] Field of Search "337/2, 3, 13, 120, 324; 200/3, ZOO/61.04, 61.05, 61.21; 219/511, 5-13, 209; 34/45 [56] References Cited UNITED STATES PATENTS 5 3,056,214 10/1962 Andersen ..34/45 3,456,505 7/1969 Schindelholz.... .....200/6l.04 X 3,233,028 2/1966 Siemianowski .200/61.05 X 2,349,519 5/1944' Reichenstein ..200/6l.21

Shaffer ..219/209 Persons ...337/324 X Osterheld..- ..219/51 1 x Primary Examiner-Bernard A. Gilheany Assistant Examiner-F. E. Bell Attorney-Charles F Voytech ABSTRACT l Clains, 3 Drawing Figures HEATER FOR PRESSURE SWITCH This invention relates to flexible diaphragm-type pressure switches.

In certain agricultural crop processing operations such as the drying of grain for storage, the operations are conducted outside to insure the rapid dissipation into the surrounding atmosphere of the moisture removed from the crop.'Such grain drying operations are presently performed by special equipment designed for this purpose, in one form of which the drying is done in batches, with automatic means for filling-and emptying-the drying bin thereof. The filling is accomplished by a horizontal auger, and its operation is terminated by the pressure of grain on a diaphragm-type pressure switch located at a point on the bin corresponding to a filled condition of the bin. Similarly, the emptying operation is accomplished by a horizontal auger the operation of which is terminated by the lack of pressure of grain on a diaphragm-type pressure switch located at or near the outlet end of the unload auger. The fill auger pressure switch is at the top of the dryer and is subjected to considerable moisture laden air rising from the drying operation. The unload auger pressure switch is at the bottom of the dryer and is subjected to a dryer air, but to more plant material. The latter falls out of the dryer and forms a frozen cruston the diaphragm which renders the diaphragm insensitive to the pressure changes produced by an emptying bin.

Thefailure of a pressure switch to function at the proper time in an automated drying operation forces a shut down of the drying operation to avoid producing improperly or insufficiently dried grain.

An object of this invention is to provide a diaphragm-type pressure switch which may be exposed to freezing moist air laden with plant material, without any impairment ofits ability to perform its designed functions.

As a-more specific object, this invention seeks to provide a diaphragm-type pressure switch,-the temperature of which, during the operation of apparatus controlled thereby, is maintained sufficiently above moisture freezing temperature to eliminate theformation of a hard crust on the diaphragm thereof, either of ice or of a combination of ice and plant material. I A

A still more specific object of this invention is the provision of a diaphragm-type pressure switch which is provided with an electric heating element and with a thermostat to control the operation of the heating element, all without altering the size or appearance of the switch. As a further specific object, this invention has within its purview the provision of a thermostatically controlled diaphragmtype switch in which the switch, heating element and thermostat a re conveniently mounted on a single cup-shaped panel which is in turn mounted in inverted position in a cup-shaped housing for maximum protection of the components of the switch.

These and other objects of this invention will become apparent from the following detailed description of a preferred form of the invention when taken together with the accompanyingdrawings in which:

FIG. 1 is a plan view of the switch of this invention as installed in the sheet metal wall of a grain dryer or the like;

FIG. 2 is a side elevational view in section of the switch being taken along line 2-2 of FIG. 1; and FIG. 3 is a plan view, partly cut away of the switch itself.

In its preferred form, this invention comprises a pressure switch incorporated in a cup-shaped housing, the open side of which is closed by an inverted cup-shaped stamping on which the switch itself, the heating element and its thermostatic control are mounted. The switch operator is a button extending through the bottom of the inverted cup in proximity to a neoprene diaphragm stretched across the open side of the housing. The central region of the diaphragm is covered on both sides with metal plates which provide stiffness for the central region and a hard surface for engagement with the switch operating button. The metal plates are disc-shaped and of smaller diameter than the diameter of the open side of the housing which leaves an annular region of the diaphragm to flex under the pressure of grain. The housing and diaphragm are secured to the side of the grain bin of the dryer over an opening therein of approximately the size of the interior of the cup-shaped housing.

Referring now to the drawings for a detailed description of the invention, the switch is shown in its entirity at 10 in FIG. 2 and is comprised of a cupshaped housing 11 having a flat side 12 which is the bottom of the cup and a cylindrical side 13 terminating in an outwardly extending attaching flange 14. Across the open side of housing 11 as defined by the attaching flange 14 is stretched a flexible diaphragm 15 preferably made of an elastomeric material such as neoprene which is capable of withstanding the moisture and temperature conditions to which the switch will be subjected. Said diaphragm 15 is circular in contour, and its edge regions which overlap the flange l4 bear against the edge regions of a circular opening 16 formed in a wall 17 of the drying apparatus to which switch 10 isapplied. Said drying apparatus may be of the type disclosed in Arthur Andersen, Jr. US. Pat. No. 3,056,214 dated Oct. 2, 1962.

The central regions of diaphragm 15 are stiffened by a pair of disc-shaped metal plates 18 and 19 disposed one on either side of said diaphragm and secured thereto by a plurality of rivets 20. Plates 18 and 19 are concentrically disposed with respect to housing 11 and are so dimensioned with reference to the circular opening 16 in wall 17 as to leave an annular section 21 of the diaphragm between said stiffening plates and circular opening 16 through which the diaphragm may be flexed in any direction transverse to the plane of plates 18 and 19. A series of screw-type fasteners 22 serves to secure housing 11 to diaphragm 15 and wall 17 together.

The open side of housing 11 is also closed by an inverted cup-shaped stamping 23 the cylindrical side 24 of which fits snugly within the cylindrical side of housing 11 and is fixed thereto by appropriate screw-type fasteners 25 disposed at intervals around the periphery of housing 11. The bottom 26 of inverted cup-shaped stamping 23 serves as a chassis on which the electrical and thermostatic elements of the switch are mounted.

Secured to bottom 26-of the inverted cup-shaped stamping 23 and on the inside of said stamping is an L-sectioned bracket 27 of sheet metal or the like, said bracket being secured to said bottom 26 in such manner that the upstanding wall 28 of the bracket is disposed near the center of said bottom 26. A micro-switch 29 of known design is disposed on one side of wall 28 and has an operating button 30 located substantially at the center of the stiffening plates 18 and 19 of diaphragm 15. Said button 30 extendsthrough an opening 30a in bottom 26.

On the opposite side of upstanding wall 28 with reference to switch 29 is secured another L-sectioned bracket 31 the upstanding wall 32 of which overlies the upstanding wall 28 of L- shaped bracket 27, and the planar wall 33 of which is substantially parallel to, and spaced from, the corresponding wall of bracket 27. Switch 29 and the upstanding walls 28 and 32 are secured together by appropriate screw-type fasteners 34.

It may be noted that a space is formed between L-sectioned bracket 31 and the cylindrical side 24 of inverted cup-shaped stamping 23. Said space is utilized to contain a resistance-type electrical heater element 35 of known design and preferably of approximately 25 watt capacity, and a fixed setting thermostat 36, also of known design, both of which are secured to planar wall 33 by appropriate screws 37 and 38, respectively.- It is contemplated that thermostat 36 will be set at approximately 40 F. and will be connected in series with heating element 35 so as to control the current thereto.

The electrical connections to the switch 29 comprise three wires 39 of a five-wire cord 40 which passes through an appropriate grommetted opening 43 (FIG. 3) in the flat side 12 of housing 1 l, and the electrical connections to the heater element 35 and thermostatic control element 36 comprise the remaining two wires 41 of said five-wire cord. It is contemplated that appropriate external controls will be used with the two wire connections 41 to supply current at volts to the heater element 35 under the desired conditions. Thus the said 1 l volt current may be supplied to the heater element for as long as the dryer of which switch 10 is a part is in operation.

The disposition of the switch 10 on the dryer will be determined by the point on a wall of the dryer at which the presence or absence of grain indicates a critical phase of the operation of the dryer. Thus one such switch and thermostatically controlled heater element may be used to indicate when agrain bin on the dryer is full of grain so that a drying operation may commence, and another may be located at the bottom of the dryer at the exit end of the grain to indicate when the bin is empty of dried grain and is ready to accept a new batch of grain for a succeeding drying operation. In both cases, the housing 11 is on the outside of the bin wall 17 and is exposed to the elements and temperature variations existing prior to, during and after a drying operation. Since the interior of housing 12 is completely sealed from the exterior, any heat losses which occur are the result of conduction through the walls of housing 12 and through the neoprene diaphragm 15. Such conduction may, if desired, be retarded by appropriate insulation (not shown) of any well-known type applied to the exterior of housing 12. The sealed interior of the switch 10 also minimizes entry of foreign particles and moisture into housing 12 and upon the electrical elements disposed therein.

With diaphragm l maintained constantly at a temperature above freezing just before and during a drying operation any material tending to adhere to the diaphragm, including moisture, will remain in a pliant or moist state and hence will not interfere with the operation of the diaphragm. Thus ice and frozen plant particles are eliminated and their formation inhibited during the operation of the dryer.

Although the foregoing invention has been described with reference to its application to a grain drying apparatus, it is diaphragm, and thermostatic means connected to the heating means to control the operation of the latter, a grain dryer bin wall having an opening therein, said diaphragm being disposed over said opening on the exterior of said wall, means for securing the housing, diaphragm and wall together, said housing being circular and said open side defining a circular cavity, a flange on the housing at the open end thereof, said diaphragm being secured to the flange and extending across said opening, a cup-shaped closure for the housing, means securing said closure to the housing in inverted relation thereto and spaced from the diaphragm, said closure having anv opening through which the switch operator extends a bracket secured to the closure and supporting the switch, and a second bracket secured to the first-mentioned bracket and supporting the heating means and the thermostatic means. 

1. In combination, an electric switch, a housing for the switch, said housing being open on one side, a flexible diaphragm covering said open side, a switch operator for said switch, said diaphragm being adapted to contact the switch operator, means within the housing for heating said diaphragm, and thermostatic means connected to the heating means to control the operation of the latter, a grain dryer bin wall having an opening therein, said diaphragm being disposed over said opening on the exterior of said wall, means for securing the housing, diaphragm and wall together, said housing being circular and said open side defining a circular cavity, a flange on the housing at the open end thereof, said diaphragm being secured to the flange and extending across said opening, a cup-shaped closure for the housing, means securing said closure to the housing in inverted relation thereto and spaced from the diaphragm, said closure having an opening through which the switch operator extends a bracket secured to the closure and supporting the switch, and a second bracket secured to the first-mentioned bracket and supporting the heating means and the thermostatic means. 